a. Field of the Invention
This invention relates to systems and methods for feeding strand under controlled conditions from a supply to utility means such as a shuttleless loom and, more specifically, it relates to strand feeding means producing an interface between a supply of strand and utility means consuming said strand.
b. Discussion of the Prior Art
In the classical shuttle loom the weft strand is inserted in the loom shed by the filling bobbin itself carried by the shuttle. The unwinding process takes place simultaneously with the passage of the bobbin through the shed, so that no specific tension problems are encountered.
Shuttleless looms incorporate new and quite radical changes in the weft insertion system. For example, since the weft strand is stationary and outside the loom, withdrawal of the strand from the supply with each pick of the loom involves alternating acceleration and deceleration of that strand. The acceleration rate is, of course, a direct reflection of the loom withdrawal process. During acceleration and deceleration the balloon created as the strand is pulled off in over-end fashion from the supply package is alternately established and collapsed. As a consequence, and in the absence suitable intermediate strand storage means, high tensions are created in the weft strand being withdrawn from its stationary supply during the acceleration phase of each pick. Such high tensions can cause sloughing and/or breakage of the weft strand being withdrawn from the supply. Moreover, loom stops can occur, and kinks can be produced in the fabric, all of which lead to reduced loom efficiency and reduced fabric quality.
Accordingly, because of the necessity to feed strand reliably from supplies at high speed into shuttleless looms and the like which operate intermittently to consume strand increments during the picking motion as just described, drum type strand storage and feeding devices are used in an attempt to reduce snarls and breakage of strand and to level tensions caused by intermittent withdrawal of strand from a supply by the loom weft insertion system. One example of such yarn storage and feeding devices is U.S. Pat. No. 3,776,480 issued to John B. Lawson on Dec. 4, 1973, which is incorporated herein as a typical background reference showing the devices and their mode of operation. These prior art storage feeders have as their objective a constant tension strand feed from the drum of the storage feeder to the strand consuming utility means.
It has also been known in the prior art to sense the store of strand on the intermediate drum of the feeder and to change the drum rotation speed by braking the drum speed whenever the store of strand becomes excessive. This technique is typified by U.S. Pat. No. 3,225,446 issued to A. G. Sarfati et al, on Dec. 28, 1965, which clutches a multiple ratio differential for accelerating and decelerating the drum speed is response to detection of a corresponding decrease or increase of strand stored thereon. Another example of such speed control is U.S. Pat. No. 3,796,385 issued to K. A. G. Jacobsson on Mar. 12, 1974, which uses a pivoting mechanical strand supply sensor and corresponding electrical contact swtich for varying the drum speed by switching on and off the a-c motor drive circuit. The drum loading and, therefore, speed can change drastically. Speed variation has been measured as much as 70% from change of friction between cold start and stable temperature conditions. Also, package tensions have been measured to vary several hundred grams. Therefore, in an effort to meet this problem it has been customary in the prior art to operate the strand storage feeder units at speeds substantially in excess of the weft consuming speed. A consequence of this has been that the strand from the supply package intermittently stops and starts, encouraging sloughing and breakage.
Prior art system designs, particularly constant torque storage feeder drive arrangements, have led to unresolved problems over wide ranges of operating conditions in the winding of strand from a supply package onto the drum of the feeder. Specifically, load changes encountered from strand package tensions and from frictional forces active in the storage feeder preclude operating at a speed generally matching the average loom withdrawal speed.
In practice with the present invention a strand feeding system between a strand supply and strand utility means such as a loom requiring strand to be fed at a first predetermined average value during operation of the utility means, i.e., a shuttleless loom is provided. The strand feeding system includes a drum arranged to receive the strand from the supply and have the strand wrapped around the drum by a flyer for temporary storage after which the strand is discharged to the loom. A balloon forms in the strand between the strand supply and the flyer during advance of the strand. A d-c variable speed motor is provided for rotating the flyer. An on-off circuit controls current flow to the motor. Speed control means are provided to establish a constant driven speed for the d-c motor in response to feedback data. Selectively adjustable voltage input means are coupled to the speed control means determining a strand feed rate from the supply which is slightly higher than the predetermined average value of strand demand by the loom. A detector serves to sense over-accumulation of strand on the drum and, in response thereto, operates the on-off circuit to interrupt current flow to the motor until said condition of over-accumulation is corrected. The on-off circuit is operated at a frequency and duration to maintain the balloon intact when current to the motor is interrupted.
Accordingly, it is a general object of this invention to resolve prior art problems of a strand storage feeder system having drum intermediate storage and tensioning control means by reducing significantly any sloughing or breakage of the strand resulting from changing drum motor drive speed or load.
This is achieved by controlling speed of operation of the strand storage feeder unit at a constant average value substantially correlated with required strand withdrawal rate, and by controlling speed variations in the strand feeding system to a frequency and duration such that the strand ballooning off the supply is maintained in its ballooning configuration.